JPS59108019A - Preparation of melamine-urea resin - Google Patents

Abstract

PURPOSE:To prepare a high-quality resin having low formalin emission, by adding 2-dimethyl- or 2-diethylaminoethanol to a mixture containing melamine, urea and HCHO at specific ratios to make the mixture alkaline, and carrying out the cocondensation of the components by keeping the mixture at a specific temperature. CONSTITUTION:A melamine-urea resin is prepared by adding 2-dimethyl- or 2- diethylaminoethanol to a mixture of 1.0mol of melamine, 4.0-4.0mol of urea and 5.5-7.5mol of HCHO thereby making the mixture alkaline state of preferably 10.0-9.0pH, and cocondensing the components at a temperature between 75 deg.C and the refluxing temperature. USE:Preparation of impregnated paper for the surface decoration of a wood board, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing melamine-urea resins for impregnated paper with low formalin release.

Impregnated paper is paper printed with woodgrain patterns or other patterns, impregnated with various resins and dried, and used as a decorative surface board for particle boards, flash boards, wood boards, etc.

Melamine resins, melamine-urea resins (hereinafter simply referred to as MU resins), and urea resins are known as the various resins mentioned above, but these resins have good physical properties such as heat resistance and chemical resistance on the surface of the decorative board. Therefore, MU resin has been widely used.

Traditionally, the manufacturing method for MU resin has been to use the raw material Lamin 1.
0.3 to 10.0 moles of urea per mole, and 3 to 10.0 moles of formaldehyde. A method has been adopted in which MU resin is produced by mixing 22.00 moles of each raw material at once, adding an alkaline substance such as sodium hydroxide, potassium hydroxide, etc., and carrying out thermal condensation.

However, the resin produced by this method had a high content of released formaldehyde, and the quality of the decorative board obtained was somewhat lacking.

The present inventors have achieved a method free of the above drawbacks by adopting a specific method.
They discovered that high quality MU resin could be obtained and completed the present invention.

By adding -1-dimethyl or 2-diethylaminoethanol to a mixture containing 5.5 to 7.3 moles of maldehyde, the mixture is made alkali.

Further, the present invention will be explained in detail.

In the present invention, melamine (hereinafter referred to as M), urea, and formaldehyde are mixed.

Then, -1-dimethylaminoethanol or -1-dimethylaminoethanol was added to the mixed aqueous solution of M, U, and F, and the pH was adjusted to 0.0-9. The temperature is adjusted to θ, and M, U, and F are co-condensed at a temperature of 73° C. to reflux.

In this operation, first formalin, which is an aqueous solution of F, is adjusted to pH 10.0 to O with Ω-dimethylaminoethanol or -1-diethylaminoethanol, and then M is added with stirring and the temperature is raised to reflux temperature.

Afterwards, add U, but if you add U all at once, the temperature of the reaction solution will drop below 70'C due to the endothermic reaction of U, and the dissolved methylolmelamine will precipitate, so add U in two parts under reflux. Thereafter, the reaction was continued at 0°C, but as the cocondensation progressed, the pH of the reaction solution gradually decreased, so dimethylaminoethanol or 2-diethylaminoethanol was added to bring the pH of the reaction solution to 7. Hold it so that it does not fall below .5.

As the reaction progresses, the reaction solution begins to exhibit a cloudiness point of 5 to 20°C, and as the reaction continues, the aqueous solution begins to exhibit a cloudiness value of /, s ~ /, 0 times, and at this point Cool the solution.

What is the cloudy point in the present invention?1. This is the temperature at which water becomes cloudy when 7 drops of a reactant are dropped into a large amount of water. The term "white turbidity value" refers to the volume ratio of the reactant to water at which, when the mixture obtained by adding water to the reactant/volume part is heated to 20° C., a white cloud appears.

Since the pH of the MU resin solution produced in this way is about 7.5, the storage stability of the MU resin bath solution for impregnated paper is at its best at pH 9, which is -9.0. Adjustments are made with dimethylaminoethanol or dimethylaminoethanol, as well as common alkaline compounds such as sodium carbonate, triethylamine, etc.

MU resin solution obtained by the production method of the present invention [, M1
For mole, U beam, O ~ g, 3 mole, F is S, S ~ 7
．． It has a composition of 3 moles. Analysis of the free formaldehyde content of this MU resin solution revealed that it was 0. /~0.3
He was in charge of weight. The amount of formaldehyde released in a decorative board produced from impregnated paper using this MU resin bath solution is the same as the amount of formaldehyde released from wood boards, and is not increased further.

F (If the number of moles of D is more than 7.j moles, the content of free formaldehyde in the obtained MU resin will be equal to or higher than the weight factor of o, g, and cosmetics using MU resin with such a high free formaldehyde content The amount of formaldehyde released from the board is increased by 2m9713 or more compared to the decorative board using the MU column resin obtained according to the present invention.

Furthermore, if the number of moles of F is less than 15 moles, there will be a shortage of F relative to M and U, and the quality of the decorative laminate manufactured from the resulting resin will be lower than that of the decorative laminate using the MU resin obtained by the present invention. It decreases in comparison.

Next, in the present invention, -1-dimethylaminoethanol or λ-diethylaminoethanol is used as a catalyst, but other alkaline catalysts such as hydroxylation)
When IJum, potassium hydroxide, sodium carbonate, triethylamine, triethanolamine, guanidine carbonate, etc. are used, the cocondensation reaction time is within fJ,yo minutes. Because of this, the free formaldehyde content in the MU resin solution is 3 to 5% by weight, and substances with extremely small and large molecular weights are unevenly contained, and the storage stability is such that it becomes cloudy within a few hours after the reaction is completed. A resin solution was obtained that was poor in .

On the other hand, when Kodimethylaminoethanol or -1diethylaminoethanol of the present invention is used, the reaction time is as long as about ioo minutes, so the free formaldehyde content becomes O0/~0.3M, and the MU resin Most of it becomes a methylolated cocondensate, and the storage stability period of the resin solution is at temperature/! ; A MU resin solution that lasted for a long time at -23°C for 75 to 20 days was obtained. The storage stability period here refers to a state in which the resin solution does not lose its transparency, does not become cloudy, and does not increase in viscosity by more than about 0.1 times the solution viscosity immediately after production. means the period of time for which it is maintained.

That is, in the present invention, a weakly alkaline kodimethylaminoethanol or 2-diethylamino-based tanol catalyst is used in a reaction system in which the number of moles of U is greater than the number of moles of M and the amount of F is small.

This shows that M, U and F are preferably co-condensed within a uniform molecular base distribution range.

Next, as the raw materials M and U used in the present invention, there is no particular need to use sheath products, and industrial standard products are sufficient. or,
For F, commercially available formalin having a weight range of 37 to 00 can be used, and it is not necessary to specifically remove methanol and formic acid contained in formalin.

Furthermore, the MU resin solution obtained according to the present invention is watered and methanol is distilled off to a non-volatile content Sθ~60% by weight and a viscosity of about Daθ~SθOP/20°C, which is easy to use in the production of impregnated paper.

In addition, known modifiers such as ethylene glycol, ε-caprolactam, toluenesulfonamide, thiourea, dicyandiamide, sugar, sodium sulfamino acid, and water-soluble nylon are added to the M and U resin solutions obtained according to the present invention. By reducing the electric power to 0, it is possible to further improve the gloss, thermal stability, denseness, elasticity, etc. of the decorative board surface and increase its quality. In addition, in the case of the present invention, since the number of moles of F relative to M and U is low, the amount of the modifier added is preferably in the range of /-5% by weight based on the total amount of M, U, and F.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

Note that the examples refer to the weight.

Example/Reactor VC37 Thiformin/! ;, 20g (1g, 7
mol) was prepared, and kodimethylaminoethanol (reagent set) A and 5 were added to adjust the pH to θ and O. Melaming ooi (3, comole) was added to the mixture while stirring, and the temperature was raised to reflux temperature (96°C).

5 minutes and 70 minutes after the start of reflux, respectively
g'(6,'z mol) of urea was added, and the temperature was then lowered to goC, and while maintaining the same temperature, formaldehyde, melamine,
Reacted with urea. 75 minutes after the start of reflux, the reaction solution had a concentration of 1
The reaction solution showed a cloudiness point of 5° C. and reached a cloudiness value of 162 times after 110 minutes, so the reaction solution was rapidly cooled while part of methanol and water was distilled off under reduced pressure.

Since the pH of this resin solution was 7.3, the pH was adjusted to 9.5 by adding an aqueous sodium carbonate solution.

The viscosity of the obtained resin solution is 0°C, and the nonvolatile content is h! i,s%.

Example Similarly to Example 1, melamine, urea, and formaldehyde were reacted. However, ethylene glycol og and 30 g of ε-caprolactam were added as modifiers before the reaction. The resulting resin solution has a high viscosity! ,00P/ko0'C
And the non-volatile content is! It was 6.3q6.

Example 3 37 diformalin igoog (22.2 mol) in the reactor
-1 diethylaminoethanol (reagent wholesaler 9)
7.3- was added to adjust the pH to 93. Add melamine 3 to this while stirring? J,9 (3.0 mol) was added and the temperature was raised to reflux temperature. 5 minutes and 10 minutes after the start of reflux, respectively, y o o i (1.7 mol) of urea was added, and the temperature was then lowered to gO ℃, and the same temperature was maintained for reaction. 5 minutes after the start of reflux. At the point when the cloudy point of the latter 3'Q is shown,
5 ml was added to Corjethylaminoethanol and then reacted. After loO minutes from the start of reflux, the white turbidity value reached 7.3 times, so the reaction solution was rapidly cooled while part of methanol and water was distilled off under reduced pressure.

Since the pH of this resin solution was 7.7, two doses of triethylamine were added to adjust the pH to 9, OK-mV. The resulting resin solution had a viscosity of qg, θ0P of 720°C, and a nonvolatile content of AO and KO.

Comparative Example/(When F is large in the present invention) A reactor was charged with 37% formalin/9kO & (211,1 mol), and 2 ml of cordimethylamine ethanol.
was added to adjust the pH to 9.g. Melamine under stirring in this,? ? A-,9 (3.0 mol) was added and the temperature was raised to reflux temperature. 5 minutes and 70 minutes after the start of reflux, respectively? ? ! ; , 9 (6.3 mol) of urea was added, and the temperature was then lowered to goC, and the reaction was carried out while maintaining the same temperature. 5 minutes after the start of reflux, it showed a white cloudy point of 5°C and 100
After a few minutes, the white cloudiness value reached twice that, so the mixture was rapidly cooled while distilling off part of the methanol and water under reduced pressure.

The pH of this resin solution was 7.5, so the pH was adjusted to 9.5 by adding 1 Irrtl of an aqueous solution of sodium carbonate. The resulting resin solution had a viscosity of 1I20P/0°C and a nonvolatile content of AiLj.

Comparative example (in the case of a catalyst other than the present invention) A reactor was charged with 37% formalin 1Sco09 (/L 7mol), and further 8ml of 3θ% sodium hydroxide aqueous solution
Add pH 9,! ; Adjusted to. To this was added melamine thiol/C 3° comol) with stirring, and the temperature was raised to reflux temperature. 5 minutes and 70 minutes after the start of reflux, respectively.
IoθJ/(17 mol) of urea was added, and the temperature was then lowered to goC, and the reaction was carried out while maintaining the same temperature. 2 from the start of reflux
It shows a cloudy point of 20℃ after 0 minutes, and a cloudiness value of 10 after 30 minutes.
When the volume reached twice its original size, it was rapidly cooled while distilling off part of the methanol and water under reduced pressure.

Since the pH of this resin solution was 7.0, 1.11% sodium carbonate aqueous solution I1. pH 9, O
K sub-adjusted. The viscosity of the resulting resin solution was 3,00F/
The temperature was 2θ°C, and the nonvolatile components were in the octopus and O range.

Reference Example 1 (Conventional method) A reactor was charged with 37 formalin/gude θl/(1 g, 1 mol) and methanol sty, and then a 30% aqueous sodium hydroxide solution was added to pH//, O
K sub-adjusted. Mix this with melamine! ; O'li (damol) and urea Koda op (+mol) were added and the temperature was raised to 35°C. The same temperature was maintained and the reaction was carried out. From 35°C for 1 hour 1S
After a few minutes, it showed a white cloudiness point of 2θ°C, and after λ time aO minutes, the white cloudiness value reached 24 times, so the pressure was reduced, methanol and water were distilled off, and the mixture was rapidly cooled.

The pH of this resin solution was 78g, so a 25% sodium carbonate aqueous solution was added to adjust the pH to 9.Examples 7-3,
A storage stability test, a free formaldehyde content analysis, a formaldehyde release test by manufacturing a decorative board, and a quality test of the decorative surface of the MU resin obtained in Comparative Example 1-C and Reference Example were conducted as follows. The results are shown in the table.

/) Storage stability test The resin is stored at room temperature between 15 and 25℃, and the viscosity is 1.
．． The number of days until it doubled was measured.

c) Free formaldehyde content analysis, analyzed by the ammonium chloride method of T Engineering SKA g O/.

3) Manufacturing method of decorative board Resin/K17 as a hardening agent CoS weight ratio para-toluenesulfonic acid aqueous solution 15-2jj9. 0.7I of sodium stearate (reagent → pumped) as a mold release agent and Nonivolta 5 (trade name, manufactured by Sanyo Chemical)-g, which is polyoxyethylene nonylphenol ether as a penetrant, were added and mixed with stirring to obtain an impregnated resin solution. . This resin solution was impregnated into g01j/m α-cellulose white base paper coated with titanium white and dried at a temperature of 2S° C. to obtain an impregnated paper.

The impregnated paper had a θ01/mj and a volatile content of 5 to bq6. Note that the volatile content is the weight loss when the impregnated paper is re-dried for S minutes at 0°C.

This impregnated paper was incorporated into the front and back surfaces of a particle board base plate with a thickness of isH, and an aluminum plate with an asbestos cushion and pear-shaped Kenreki finish was hot-pressed using a caulk plate at /AO℃.
20 K/cy/l.

A decorative board was produced by hot pressing for 3 minutes. Return cooling press after hot pressing was not performed.

ri) Measurement of released formaldehyde J: AA; 90. The amount of formaldehyde released was measured by the acetylacetone method. The particle board base plate was manufactured using urea resin as an adhesive.

S) Quality test of decorative surface a. Appearance: The condition and gloss of the decorative surface were judged with the naked eye.

b. Acid resistance 20. The degree of action of 2N hydrochloric acid on the decorative surface in 1 gu hour was determined.

C Heat Resistance = It was determined whether or not cracks were formed by heating at 70° C. for 20 hours using D Tech Nk3799.

d Water resistance: D Engineering N! 3? 9? Determined by water vapor test.

e Stainability: After applying black shoe polish, the degree of sealing was determined by wiping.

The determination of a%e is on a scale of 1 to O, with / indicating extremely good and 6 indicating completely poor.

The results in the λ7 table show that the MU resin according to the present invention released the same amount of form7/l/dehyde as the particle board script, and did not increase it.

In addition, the surface quality evaluation of decorative laminates made of MU resin with a higher U content than M content as in the present invention is generally on a scale of 3.
The following is considered suitable for coating the front and back surfaces, and it was confirmed that the quality of the decorative board obtained by the present invention satisfies this.

Furthermore, the storage stability of the MU resin solution is also /j days or more, which does not pose any problem in industrial implementation.

Applicant: Nippon Kasei Co., Ltd. Representative Patent Attorney Hase - (7 others)

Claims (1)

[Claims] (1) 1.0 mol of melamine, 4.0-4.5 mol of urea and formaldehyde! , a method for producing a melamine-urea resin by adding 2-dimethyl or cordiethylaminoethanol to the mixture in a proportion of 5 to 7.5 moles.